My AppVeyor config now tests Perl 6 on Linux too

AppVeyor now supports Ubuntu along with Windows. I’ve updated my Perl 6 AppVeyor config example to include that. I created a chocolatey package for Rakudo Star to make it easier to test on AppVeyor. I think there are some Rakudo Star packages for linux in the future and that will make the linux side even easier and faster. At the moment it takes about 20 minutes to build before you get to the tests.